Gene maps of three deadly parasites 'nearly complete'

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[RIO DE JANEIRO] Researchers say they are close to completing 'genetic maps' of the parasites responsible for three of the developing world's most insidious diseases — sleeping sickness, cutaneous leishmaniasis and Chagas disease.

The researchers expect that the maps, detailing the structure of each parasite's DNA, will stimulate the development of vaccines, drugs and tools that will allow rapid diagnosis of infections.

"The sequencing is practically concluded and a final draft will soon be made available to researchers worldwide," says molecular biologist Wim Degrave, a senior researcher at Brazil's Oswaldo Cruz Foundation.

The foundation is one of a number of institutions in Brazil and other countries in the international consortium that has spearheaded the research on Trypanosoma cruzi, the parasite that causes Chagas disease. The consortium is led by the US-based Seattle Biomedical Research Institute and The Institute for Genomic Research, and the Karolinska Institute in Sweden.
Degrave and colleagues at other Brazilian institutions, including the University of São Paulo and the Federal University of São Paulo had to overcome a number of obstacles during the sequencing process. Degrave told SciDev.Net that the parasite's genetic material contains many fragments and repeated sequences that made mapping the entire genetic code — or genome — difficult.

In September, preliminary versions of the maps were presented at the 'TriTryp Genome Meeting' in Seattle, Washington, United States. The sequence data has been available through the websites of The Institute for Genomic Research and the Wellcome Trust Sanger Institute in Cambridge, United Kingdom.

There are eight million chronic cases of Chagas disease in Brazil alone. Transmitted by the bite of so-called 'assassin bugs', the disease damages the heart and digestive tract.

Related parasites whose genomes are also being sequenced are Trypanosoma brucei, which causes sleeping sickness in Africa and Leishmania major, which is responsible for cutaneous leishmaniasis, a disease that causes ulcer-like lesions in the skin.

The laboratories that participated in the sequencing are now initiating studies of how each parasite's function and interact. In Latin America, groups from Brazil, Venezuela and Argentina are already working on this task.

"Through the construction and analysis of the genome sequence in the computer, it is possible to predict the probable function of 60 per cent of the proteins [the parasite produces] and to study the interaction of these parasites with their hosts and the environment," says Degrave.

The researchers are using software that allows functions to be attributed to genetic sequences and to compare the genomes in order to discover similarities among the parasites. This study is focusing on identifying biological processes common to the three species and developing drugs to inhibit them — perhaps even one drug that will work against all three parasites.